more mobile docs

docs/assets/css/docs.css

@@ -57,6 +57,13 @@ body {
   top: 20px;
   color: #fff;
   cursor: pointer;
+  -webkit-transition: opacity 0.2s linear;
+  -moz-transition: opacity 0.2s linear;
+  transition: opacity 0.2s linear;
+}
+.docs-nav:active {
+  color: #fff;
+  opacity: .5;
 }
 
 .docs-logo {

sass/docs.scss

@@ -56,6 +56,12 @@ body {
   top: 20px;
   color: #fff;
   cursor: pointer;
+  @include transition(opacity .2s linear);
+
+  &:active {
+    color: #fff;
+    opacity: .5;
+  }
 }
 .docs-logo {
   width: 75px;